Various types of wrenches having adjustable jaws to grip a range of sizes or diameters of bolts, nuts or other fasteners have been provided with varying degrees of acceptance. Examples of adjustable jaw wrenches include open jaw types wherein the fastener is typically approached from a side and the jaws are then manually adjusted for size to fit a work piece. Ratchet action adjustable jaw wrenches typically approach the fastener from the top and then the jaws are adjusted for size to snuggly fit the fastener. The mechanisms vary in the prior art for tightening the jaws up against a work piece fastener. Adjustable jaw ratchet action wrenches typically have an annularly mounted mechanism wherein a rotatable element adjusts the jaws inwardly or outwardly to match the size of the work piece fastener. One such prior art wrench taught by Fossella (U.S. Pat. No. 5,207,127) is typical of adjustable jaw ratchet action wrenches wherein jaw elements are opposingly and slidably mounted in radial guide slots in an annularly shaped control disc coaxially positioned in the housing of the wrench. The mounted jaws elements are thrust inwardly towards the central axis of the housing by rotating an adjacent adjustment disc wherein a cam follower portion on each jaw element interacts and travels through a concentrically positioned and arch-shaped cam groove in the adjustment disc. The cam grooves have one end closer to the axis of the wrench such that when the adjustment disc is rotated in one direction the jaws elements move towards the central axis whitest turning the adjustment disc in the opposing direction moves the jaw elements away from the axis. The jaw elements have a grasping feature extending perpendicularly to the adjustment and control discs such that a centrally presented work piece is captured by opposing jaw elements by the rotation of the adjustment disc. Prior art wrenches, as this one, utilize a set of ratchet teeth on the periphery of the control disc to engage a ratchet pawl on the wrench handle thereby causing the control disc to rotate with the housing and handle. It will be appreciated that as the wrench handle is rotated, force is transferred by the ratchet pawl to the control disc, then through the cam followers held in position by the adjustment disc on the jaw elements to the gripping features of the jaw elements and finally to the work piece.
These typical prior art wrench structures present a number of disadvantages. Firstly, opening the jaws is accomplished by rotating the adjustment disc in one direction and closing the jaws requires a rotation motion in the reverse direction. In other words, the grasping is unidirectional. Further, the structure necessitates the application of similar torque levels transferred to the adjustment disc in both rotation directions for the corresponding cam surfaces to push the jaw elements in the corresponding direction thereby making certain application of the tool ineffective. Additionally, because the jaw elements are disposed perpendicularly from the control and adjustment discs, the transference of force through to the grip surface creates a cantilevering of the jaw elements generating additional frictional forces impeding operation, increasing wear of the wrench components and reduces the durability of the tool. The cantilevering further eventually widens the cam grooves which consequently affects the matching of the grip surfaces of the jaw elements with the work piece yet further impeding the operation by increasing the opportunities for the tool to bind. Of particular noteworthiness is the load transfer through the control disc wherein application of torque to the handle causes a high level of cantilever load on both the control and adjustment discs therefore necessitating hard or harden materials for their construction thereby increasing weight and manufacturing costs over lighter materials. Finally, a separate ratcheting means is often included between the control and adjustment discs to prevent their relative rotation so as to retain the jaw elements in position during the free return stroke of the wrench handle thereby necessitating significant complications to the tool design.